This is a note to let you know that I've just added the patch titled
asm-generic/tlb: avoid potential double flush to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: asm-generic-tlb-avoid-potential-double-flush.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <sta...@vger.kernel.org> know about it. >From foo@baz Mon Jan 4 01:45:29 PM CET 2021 From: Santosh Sivaraj <sant...@fossix.org> Date: Thu, 12 Mar 2020 18:57:40 +0530 Subject: asm-generic/tlb: avoid potential double flush To: <sta...@vger.kernel.org>, linuxppc-dev <linuxppc-dev@lists.ozlabs.org> Cc: Michael Ellerman <m...@ellerman.id.au>, Greg KH <g...@kroah.com>, Sasha Levin <sas...@kernel.org>, Peter Zijlstra <pet...@infradead.org>, "Aneesh Kumar K . V" <aneesh.ku...@linux.ibm.com> Message-ID: <20200312132740.225241-7-sant...@fossix.org> From: Peter Zijlstra <pet...@infradead.org> commit 0758cd8304942292e95a0f750c374533db378b32 upstream. Aneesh reported that: tlb_flush_mmu() tlb_flush_mmu_tlbonly() tlb_flush() <-- #1 tlb_flush_mmu_free() tlb_table_flush() tlb_table_invalidate() tlb_flush_mmu_tlbonly() tlb_flush() <-- #2 does two TLBIs when tlb->fullmm, because __tlb_reset_range() will not clear tlb->end in that case. Observe that any caller to __tlb_adjust_range() also sets at least one of the tlb->freed_tables || tlb->cleared_p* bits, and those are unconditionally cleared by __tlb_reset_range(). Change the condition for actually issuing TLBI to having one of those bits set, as opposed to having tlb->end != 0. Link: http://lkml.kernel.org/r/20200116064531.483522-4-aneesh.ku...@linux.ibm.com Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com> Reported-by: "Aneesh Kumar K.V" <aneesh.ku...@linux.ibm.com> Cc: <sta...@vger.kernel.org> # 4.19 Signed-off-by: Santosh Sivaraj <sant...@fossix.org> [santosh: backported to 4.19 stable] Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- include/asm-generic/tlb.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/include/asm-generic/tlb.h +++ b/include/asm-generic/tlb.h @@ -179,7 +179,12 @@ static inline void __tlb_reset_range(str static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb) { - if (!tlb->end) + /* + * Anything calling __tlb_adjust_range() also sets at least one of + * these bits. + */ + if (!(tlb->freed_tables || tlb->cleared_ptes || tlb->cleared_pmds || + tlb->cleared_puds || tlb->cleared_p4ds)) return; tlb_flush(tlb); Patches currently in stable-queue which might be from sant...@fossix.org are queue-4.19/asm-generic-tlb-track-which-levels-of-the-page-tables-have-been-cleared.patch queue-4.19/asm-generic-tlb-track-freeing-of-page-table-directories-in-struct-mmu_gather.patch queue-4.19/asm-generic-tlb-avoid-potential-double-flush.patch queue-4.19/mm-mmu_gather-invalidate-tlb-correctly-on-batch-allocation-failure-and-flush.patch queue-4.19/powerpc-mmu_gather-enable-rcu_table_free-even-for-smp-case.patch queue-4.19/asm-generic-tlb-arch-invert-config_have_rcu_table_invalidate.patch